1. Field of the Invention
The present invention is directed to a flat cathode ray tube which has a container with a cathodo-luminescent layer on one surface and guides a beam of electron along a sinuous path to a point for direction against the luminescent layer.
2. Description of the Prior Art
Among the plurality of previously discussed concepts for a flat display screen, a display which operates on a gas discharge basis appears to have the best prospects for success. If color moving pictures are displayed, this is particularly true. A structure, which is especially promising for a flat display screen utilizes a gas filled envelope which is sub-divided by means of a control structure into a front and back space. The control structure consists of perforated row conductors and perforated column conductors with the row conductors facing a surface cathode which is provided on a back surface of the envelope while the column conductors are turned or directed towards the front surface of the envelope which is provided with luminescent layer and a post deflection acceleration anode. The spacing between the column conductors and the acceleration anode is so small that even with a potential difference of several kV, no gas discharge is brought about. In operation, an approximately wedge-shaped gas discharge burns between the surface cathode and the row which has been selected and the column conductors obtain signal voltages which either block electrons of the gas discharge or draw them through the openings of the control structure into the front space. These electrons are accelerated by the acceleration anode and strike the luminescent screen or layer to generate a luminous spot at the location of impact. A description of the above structure is found in my U.S. Pat. No. 3,956,667 which was based on German O.S. No. 2,412,869. The operation of the structure is explained in greater detail in the disclosure of the U.S. Patent which is incorporated herein by reference.
With the display principles which have been described hereinabove, television pictures, which are already colored can be generated with a quite promising optical quality. However, previously built displays do not yet function with sufficient reliability because of the problems, which are connected with the gas filling of the envelope, cathode sputtering, fluctuations in the gas pressure, dangers of arc-through which will occur with the necessary high accleration voltages that are required after the deflection step. These problems with reliability of these screens has not yet been satisfactorily solved.
The above noted difficulties are eliminated when one does not use a gas discharge as an electron source but rather uses a common cathode as in the case for example of a panel type display disclosed in U.S. Pat. No. 4,103,204. In the case of this embodiment, a cathode, which is extended parallel to the direction of a row releases a multiplicity of point-form electron beams which number will correspond to the column count of a picture matrix. In the beam guidance space, the individual beams are kept on sinuous paths with the electrons moving around wires which run parallel to the row and the common cathode. In the framework of this proposal, a row sequential addressing can be accomplished by deflecting the beams row for row and each of the beams can receive information by means of modulation of the electron source.
Such a system offers a number of advantages, a cathode requires a small surface and therefore only a small quantity of heat can be radiated and little cathode material will be vaporized. In addition, there is a very small structural depth for the number of vibrations in the sinuous path which are carried out by electron beams corresponds to the count of the row. In accordance with this, the height of amplitude of the vibration measurement for the beam for the thickness of the beam guidance space has a value similar to that of the row spacing. However, these advantages are opposed by an important disadvantage. The "slalom focusing" which is used and discussed in great detail in the article by J. S. Cook et al, "Slalom Focusing", Proceedings of the IRE, November, 1957, pp. 1517-22 requires an especially precise dimensioning which significantly increases the manufacturing cost. This is particularly in the case of a display with a fine raster of picture points and corresponding filigree construction. Due to these costs, it is estimated that the standard size television screen of this structure can only be manufactured with an unacceptable high expenditure in manufacturing costs.